chore: re-add sanitized demo GIF

Author: greynewell

demos/demo.gif

@@ -0,0 +1 @@
+literal:/Users/graphtheory==>/Users/graphtheory

filter-repo-replacements.txt

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+# Remove demo media (and optional path replacements) from entire git history.
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+cd "$ROOT"
+
+if ! command -v git-filter-repo >/dev/null 2>&1; then
+  echo "Install: python3 -m pip install git-filter-repo" >&2
+  exit 1
+fi
+
+ORIGIN=""
+git remote get-url origin >/dev/null 2>&1 && ORIGIN="$(git remote get-url origin)"
+
+INVERT=()
+[[ -e demos/demo.gif ]] && INVERT+=(--path demos/demo.gif)
+[[ -d demos/vhs/out ]] && INVERT+=(--path demos/vhs/out)
+[[ -d assets/demos ]] && INVERT+=(--path assets/demos)
+
+if ((${#INVERT[@]} > 0)); then
+  echo "filter-repo: removing demo blobs from all commits"
+  git filter-repo --invert-paths "${INVERT[@]}" --force
+  [[ -n "$ORIGIN" ]] && git remote add origin "$ORIGIN"
+fi
+
+if [[ -f filter-repo-replacements.txt ]]; then
+  echo "filter-repo: replace-text from filter-repo-replacements.txt"
+  git filter-repo --replace-text filter-repo-replacements.txt --force
+  [[ -n "$ORIGIN" ]] && git remote add origin "$ORIGIN"
+fi
+
+echo "History rewrite complete. Add clean demos, commit, then:"
+echo "  git push --force-with-lease origin main"